In recent years, effects of contamination of mothers' milk especially by dioxins, which are carcinogens, endocrine-disrupting chemicals and the like on infants have given rise to a serious social concern throughout the world. A great majority of these contaminants led by dioxins and including endocrine-disrupting chemicals are soluble in fat so that, once they are uptaken in the body, they are mostly stored in adipose tissues although extremely small fractions of them are discharged into excrement via bile. As body fat is mobilized upon synthesis of milk fat in the mammary glands, the contaminants stored in the fatty tissues transfer into milk. As a result, milk acts as a principal discharge route for contaminants led by dioxins and including endocrine-disrupting chemicals. Collection of human milk in a standardized method is, therefore, a useful means for the detection of these exogeneous toxic substances. Further, milk expression or suction becomes necessary for the purpose of treatment if any morbid abnormality is observed in the quality of milk for one reason or another and breast feeding has to be discontinued or if an intrammary accumulation of any non-milk morbid product is ascertained.
It is, however, the current circumstances that no useful breast pump is available for the collection of human milk in a standardized universal manner and expression of milk is manually conducted at every medical institution. Hence, collection of human milk is hardly considered to be performed adequately in a standardized universal manner. For example, the pulsating suction breast pump disclosed in JP-A-11-178917 includes a teat cup secured on a free end of a cylinder such that a suction pressure is intermittently produced within the teat cup by reciprocations of a piston. However, this breast pump is complex in mechanism, has difficulty in adjusting the pulsation cycle, and lacks flexibility. Further, it is difficult to disassemble and wash this breast pump, and moreover, it is essential to use a sealing packing in direct contact with a milk expressing passageway. There is, accordingly, a potential risk that the sealing packing may become a cause of bacterial growth unless thorough washing is conducted.
In the breast pump which is disclosed in JP-A-2000-511443 and is capable of double-breast pumping, a reduced pressure is periodically produced by a mechanism equipped with a diaphragm pump instead of a piston-cylinder means so that this breast pump is simplified to some extent in mechanism. However, a milk expressing member which is attached to a collection container is of a type that the milk expressing member is provided at a lower extremity thereof, where the milk expressing member is inserted into the collection container, with an on/off valve, and has a construction such that at the time of a reduced pressure, the interior of a teat cup is brought into a state reduced in pressure and the on/off valve is closed but at the time of atmospheric pressure, the on/off valve is opened by the expressed human milk to collect it in the collection container. In addition to a need for a complex mechanism for the assembly of the on/off valve, it is necessary to arrange within the milk expressing member such a complex partition that upon expressing milk, permits passage of air therethrough but does not permit passage of human milk to the side of the diaphragm pump. Therefore, it is difficult to wash the inside of the milk expressing member, and moreover, the on/off valve involves a potential risk that it may become a cause of bacterial growth.
Further, these breast pumps are each of the construction that the inner wall of the teat cup is brought in its entirety into direct contact with the breast to directly apply a negative pressure there. A stimulation by the negative pressure is, therefore, different from a suckling stimulation by an infant, that is, an actual suckling stimulation which acts only on the areola and nipple of the mother's breast, and moreover, expression of milk is not considered to proceed smoothly.
With the foregoing circumstances in view, the object of the present invention is to provide a novel breast pump, which permits universal expression of milk from the human breast without being affected by a personal difference of a person who performs the expression of milk. In addition, the another object of the present invention is to provide a novel breast pump, which is simple in construction, permits easy washing of the inside of a milk expressing member, and can avoid inconveniences such as bacterial growth. Furthermore, the further object of the present invention is to provide a novel breast pump, which is designed to permit an application of similar stimulations as suckling stimulations by an infant to the areola and nipple of the mother's breast so that smooth expression of milk can be performed.